diff --git a/src/codesnap/htmlconverter.py b/src/codesnap/htmlconverter.py
index 3c99e4ba..225e58c8 100644
--- a/src/codesnap/htmlconverter.py
+++ b/src/codesnap/htmlconverter.py
@@ -7,39 +7,6 @@
 from string import Template
 
 
-colors = ['#e6194B', '#3cb44b', '#ffe119', '#4363d8', '#f58231', '#42d4f4',
-          '#f032e6', '#bfef45', '#fabed4', '#469990', '#dcbeff', '#9A6324',
-          '#fffac8', '#aaffc3', '#808000', '#ffd8b1']
-
-
-def string_to_color(s):
-    return colors[hash(s) % len(colors)]
-
-
-def snap_tree_node_html(node, parent_entry, parent_exit):
-    parent_duration = parent_exit - parent_entry
-    left = (node.t_entry - parent_entry) / parent_duration
-    width = (node.t_exit - node.t_entry) / parent_duration
-    ret = '<div style="left:{}%;width:{}%;" class="func-container">'.\
-        format(left*100, width*100)
-    ret += '<div style="background-color:{};" class="func-block">{}</div>'.\
-        format(string_to_color(node.function_name), html.escape(node.function_name))
-    for child in node.children:
-        ret += child.html(node.t_entry, node.t_exit)
-    ret += '</div>'
-
-    return ret
-
-
-def snap_tree_root_node_html(node):
-    ret = '<div id="root" style="width:98vw;margin-left:1vw">'
-    for child in node.children:
-        ret += child.html(node.t_entry, node.t_exit)
-    ret += '</div>'
-
-    return ret
-
-
 def generate_html_report_from_snap_tree(tree):
     sub = {}
 
diff --git a/src/codesnap/snaptree.py b/src/codesnap/snaptree.py
index 9f96e982..dc0750ec 100644
--- a/src/codesnap/snaptree.py
+++ b/src/codesnap/snaptree.py
@@ -1,7 +1,7 @@
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/gaogaotiantian/codesnap/blob/master/NOTICE.txt
 
-from .htmlconverter import snap_tree_node_html, snap_tree_root_node_html, generate_html_report_from_snap_tree
+from .htmlconverter import generate_html_report_from_snap_tree
 
 
 class SnapTreeNode:
@@ -13,15 +13,6 @@ def __init__(self, parent, name, t_entry, t_exit):
         self.exited = False
         self.children = []
 
-    def html(self, parent_entry=None, parent_exit=None):
-        if parent_entry is None and parent_exit is None:
-            # This is root
-            return snap_tree_root_node_html(self)
-        elif self.exited:
-            return snap_tree_node_html(self, parent_entry, parent_exit)
-        else:
-            return ""
-
     def json_object(self):
         stack = [self]
         ret = []
diff --git a/tests/test_cmdline.py b/tests/test_cmdline.py
new file mode 100644
index 00000000..83a610ac
--- /dev/null
+++ b/tests/test_cmdline.py
@@ -0,0 +1,40 @@
+import unittest
+import subprocess
+import os
+
+file_content = \
+"""
+def fib(n):
+    if n < 2:
+        return 1
+    return fib(n-1) + fib(n-2)
+fib(5)
+"""
+class TestCommandLineBasic(unittest.TestCase):
+    def build_script(self):
+        with open("cmdline_test.py", "w") as f:
+            f.write(file_content)
+
+    def cleanup(self, output_file="result.html"):
+        os.remove("cmdline_test.py")
+        os.remove(output_file)
+
+    def template(self, cmd_list, expected_output_file="result.html", success=True):
+        self.build_script()
+        result = subprocess.run(cmd_list)
+        self.assertTrue(success ^ (result.returncode != 0))
+        self.assertTrue(os.path.exists(expected_output_file))
+        self.cleanup(output_file=expected_output_file)
+
+    def test_run(self):
+        self.template(["python", "-m", "codesnap", "cmdline_test.py"])
+    
+    def test_outputfile(self):
+        self.template(["python", "-m", "codesnap", "-o", "result.html", "cmdline_test.py"])
+        self.template(["python", "-m", "codesnap", "-o", "result.json", "cmdline_test.py"], expected_output_file="result.json")
+        self.template(["python", "-m", "codesnap", "--output_file", "result.html", "cmdline_test.py"])
+        self.template(["python", "-m", "codesnap", "--output_file", "result.json", "cmdline_test.py"], expected_output_file="result.json")
+    
+    def test_tracer(self):
+        self.template(["python", "-m", "codesnap", "--tracer", "c", "cmdline_test.py"])
+        self.template(["python", "-m", "codesnap", "--tracer", "python", "cmdline_test.py"])
\ No newline at end of file
diff --git a/tests/test_performance.py b/tests/test_performance.py
index 80855906..7ce67121 100644
--- a/tests/test_performance.py
+++ b/tests/test_performance.py
@@ -12,8 +12,8 @@ def do_one_function(self, func):
         func()
         origin_end = time.perf_counter()
 
-        # With codesnap
-        snap = CodeSnap()
+        # With codesnap + python tracer
+        snap = CodeSnap("python")
         snap.start()
         instrumented_start = time.perf_counter()
         func()
diff --git a/tests/test_regression.py b/tests/test_regression.py
index de9912be..9d9f56ee 100644
--- a/tests/test_regression.py
+++ b/tests/test_regression.py
@@ -11,3 +11,11 @@ def test_datetime(self):
         snap.stop()
         snap.parse()
         snap.generate_json()
+
+        snap = codesnap.CodeSnap(tracer="python")
+        snap.start()
+        from datetime import timedelta
+        timedelta(hours=5)
+        snap.stop()
+        snap.parse()
+        snap.generate_json()
\ No newline at end of file